feat: Refactor SMTP client to support session-based email processing, enhancing queue management and error handling

.gitignore

@@ -6,6 +6,8 @@ yarn-error.log*
 
 # Build outputs
 lib/
+lib-esm/
+
 dist/
 *.tsbuildinfo
 

README.md

@@ -1,122 +1,232 @@
-# @siwatsystem/mxrelay-consumer
+# @siwats/mxrelay-consumer
 
 [![TypeScript](https://img.shields.io/badge/%3C%2F%3E-TypeScript-%230074c1.svg)](http://www.typescriptlang.org/)
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
-A production-ready TypeScript client library for SMTP over WebSocket protocol with intelligent queue management, automatic reconnection, and comprehensive error handling. Includes full Nodemailer transport compatibility.
+A production-ready TypeScript client library for SMTP over WebSocket protocol with **session-based queue management**, automatic reconnection, and comprehensive error handling. Features proper SMTP session protocol implementation with mutex-based session locking.
 
-## Features
+## 🚀 Key Features
 
-**Intelligent Queue Management**
+### **Session-Based SMTP Protocol**
-- Automatic WebSocket connection when messages are queued
+- **Proper SMTP Sessions**: One session = EHLO → AUTH → Multiple Emails → QUIT
-- Priority-based message processing (CRITICAL > HIGH > NORMAL > LOW)
+- **Session Mutex**: Only one SMTP session active at a time (protocol compliant)
-- Configurable queue limits and overflow protection
+- **Email Batching**: Send multiple emails efficiently within a single session
-- Auto-disconnect when queue is empty
+- **Resource Optimization**: Connect only when needed, disconnect when idle
 
-**Robust Connection Handling** 
+### **Intelligent Queue Management**
-- Automatic reconnection with exponential backoff
+- **Session Queuing**: Queues complete email sessions, not individual commands
-- Connection state management and lifecycle
+- **Priority-Based Processing**: CRITICAL > HIGH > NORMAL > LOW priority levels
-- Heartbeat monitoring and timeout handling
+- **Configurable Batching**: Control emails per session with `maxEmailsPerSession`
-- Graceful connection recovery
+- **Smart Resource Usage**: Auto-connect/disconnect based on queue state
 
-**High Performance**
+### **Production-Ready Reliability**
-- Efficient SMTP channel cycling per message
+- **Comprehensive Error Handling**: Structured error classification and meaningful messages
-- Minimal resource usage with smart connection management
+- **Automatic Reconnection**: Exponential backoff with configurable retry limits
-- Concurrent message processing support
+- **Timeout Management**: Session, email, and connection-level timeouts
-- Optimized WebSocket communication
+- **Connection State Management**: Full lifecycle state tracking
 
-**Enterprise-Grade Reliability**
+### **Nodemailer Integration**
-- Comprehensive SMTP error handling with meaningful messages
+- **Full Nodemailer Compatibility**: Drop-in replacement for existing transports
-- Timeout management for all operations
+- **Standard API**: Use familiar Nodemailer methods and options
-- Retry logic with configurable attempts
+- **Advanced Features**: Attachments, HTML, multipart messages, custom headers
-- Structured error classification
 
-**Nodemailer Integration**
+## 📊 Architecture Overview
-- Full Nodemailer transport compatibility
-- Transparent bridge for all email features
-- Support for attachments, HTML, multipart messages
-- Standard Nodemailer API compatibility
 
-## Installation
+```mermaid
+graph TB
+    subgraph "Client Application"
+        App[Your Application]
+        NM[Nodemailer]
+        Transport[SMTPWSTransport]
+    end
     
-```bash
+    subgraph "Session Management"
-npm install @siwatsystem/mxrelay-consumer
+        Client[SMTPOverWSClient]
-# or
+        Queue[Session Queue]
-bun add @siwatsystem/mxrelay-consumer
+        SM[Session Manager]
+    end
+    
+    subgraph "Protocol Layer"
+        WS[WebSocket Connection]
+        Auth[Authentication]
+        Channel[SMTP Channel]
+    end
+    
+    subgraph "Remote Server"
+        Relay[SMTP WebSocket Relay]
+        SMTP[SMTP Server]
+    end
+    
+    App --> NM
+    NM --> Transport
+    Transport --> Client
+    Client --> Queue
+    Queue --> SM
+    SM --> WS
+    WS --> Auth
+    Auth --> Channel
+    Channel --> Relay
+    Relay --> SMTP
+    
+    style Client fill:#e1f5fe
+    style Queue fill:#f3e5f5
+    style SM fill:#fff3e0
+    style Channel fill:#e8f5e8
 ```
 
-## Quick Start
+## 🔄 Session Processing Flow
 
-### Direct Client Usage
+```mermaid
+sequenceDiagram
+    participant App as Application
+    participant Client as SMTPOverWSClient
+    participant Queue as Session Queue
+    participant WS as WebSocket
+    participant Server as SMTP Server
+    
+    Note over App,Server: Email Submission
+    App->>Client: queueEmail(from, to[], data)
+    Client->>Queue: Add to session or create new
+    
+    Note over App,Server: Session Processing (Mutex)
+    Queue->>Client: Process next session
+    Client->>WS: Connect (if needed)
+    WS->>Server: WebSocket connection
+    Server-->>WS: Connection established
+    
+    Client->>Server: AUTHENTICATE
+    Server-->>Client: AUTH_SUCCESS
+    
+    Client->>Server: SMTP_CHANNEL_OPEN
+    Server-->>Client: SMTP_CHANNEL_READY
+    Server-->>Client: 220 SMTP ready
+    
+    Client->>Server: EHLO client
+    Server-->>Client: 250 EHLO OK
+    
+    Client->>Server: AUTH PLAIN <credentials>
+    Server-->>Client: 235 AUTH OK
+    
+    loop For each email in session
+        Client->>Server: MAIL FROM:<sender>
+        Server-->>Client: 250 Sender OK
+        
+        Client->>Server: RCPT TO:<recipient>
+        Server-->>Client: 250 Recipient OK
+        
+        Client->>Server: DATA
+        Server-->>Client: 354 Start data
+        
+        Client->>Server: <email content>\r\n.
+        Server-->>Client: 250 Message accepted
+        
+        Client->>App: Email resolved
+    end
+    
+    Client->>Server: QUIT
+    Server-->>Client: 221 Goodbye
+    
+    Client->>Server: SMTP_CHANNEL_CLOSE
+    WS->>WS: Disconnect (if queue empty)
+    
+    Client->>App: Session completed
+```
+
+## 📦 Installation
+
+```bash
+npm install @siwats/mxrelay-consumer
+# or
+bun add @siwats/mxrelay-consumer
+```
+
+## 🚀 Quick Start
+
+### Direct Client Usage (New Session-Based API)
 
 ```typescript
-import { SMTPOverWSClient } from '@siwatsystem/mxrelay-consumer';
+import { SMTPOverWSClient } from '@siwats/mxrelay-consumer';
 
 const client = new SMTPOverWSClient({
     url: 'wss://api.siwatsystem.com/smtp',
     apiKey: 'your-api-key',
-    debug: true
+    debug: true,
+    maxEmailsPerSession: 5,  // Batch up to 5 emails per session
+    sessionTimeout: 300000   // 5 minute session timeout
 });
 
-// Send SMTP commands directly
+// Queue individual emails - they'll be batched into sessions automatically
 try {
-    const response = await client.sendSMTPCommand(`
+    // These emails will be sent in the same SMTP session
-        MAIL FROM: <sender@example.com>
+    const emailId1 = await client.queueEmail(
-        RCPT TO: <recipient@example.com>
+        'sender@example.com',
-        DATA
+        ['recipient1@example.com'],
-        Subject: Test Email
+        'Subject: Email 1\r\n\r\nFirst email content'
+    );
     
-        Hello from SMTP over WebSocket!
+    const emailId2 = await client.queueEmail(
-        .
+        'sender@example.com', 
-        QUIT
+        ['recipient2@example.com'],
-    `);
+        'Subject: Email 2\r\n\r\nSecond email content'
-    console.log('Email sent:', response);
+    );
+    
+    console.log('Emails queued:', emailId1, emailId2);
 } catch (error) {
-    console.error('SMTP error:', error.message);
+    console.error('Email error:', error.message);
 } finally {
     await client.shutdown();
 }
 ```
 
-### Nodemailer Transport
+### Nodemailer Transport (Recommended)
 
 ```typescript
 import nodemailer from 'nodemailer';
-import { createTransport } from '@siwatsystem/mxrelay-consumer';
+import { createTransport } from '@siwats/mxrelay-consumer';
 
-// Create transport (uses defaults: api.siwatsystem.com:443 secure)
+// Create transport with session batching
-const transport = createTransport('your-api-key');
-
-// Or with custom options
 const transport = createTransport('your-api-key', {
-    host: 'custom.server.com',
+    host: 'api.siwatsystem.com',
-    port: 80,
+    port: 443,
-    secure: false,
+    secure: true,
-    debug: true
+    debug: true,
+    maxEmailsPerSession: 10,    // Batch up to 10 emails per session
+    sessionBatchTimeout: 2000   // Wait 2 seconds to batch emails
 });
 
 const transporter = nodemailer.createTransporter(transport);
 
-// Send email using standard Nodemailer API
+// Send multiple emails - automatically batched into sessions
-const info = await transporter.sendMail({
+const emails = [
-    from: 'sender@example.com',
-    to: 'recipient@example.com',
-    subject: 'Test Email via SMTP WebSocket',
-    text: 'Plain text version',
-    html: '<h1>HTML version</h1>',
-    attachments: [
     {
-            filename: 'document.pdf',
+        from: 'sender@example.com',
-            path: './document.pdf'
+        to: 'user1@example.com',
+        subject: 'Welcome Email',
+        html: '<h1>Welcome to our service!</h1>'
+    },
+    {
+        from: 'sender@example.com',
+        to: 'user2@example.com', 
+        subject: 'Newsletter',
+        html: '<h1>Monthly Newsletter</h1>',
+        attachments: [{ filename: 'report.pdf', path: './report.pdf' }]
     }
-    ]
+];
-});
+
+// Send all emails - they'll be efficiently batched into SMTP sessions
+for (const email of emails) {
+    try {
+        const info = await transporter.sendMail(email);
+        console.log('Email sent:', info.messageId);
+    } catch (error) {
+        console.error('Failed to send email:', error.message);
+    }
+}
 
-console.log('Message sent:', info.messageId);
 await transport.close();
 ```
 
-## Configuration
+## ⚙️ Configuration
 
 ### Client Configuration
 
@@ -124,172 +234,348 @@ await transport.close();
 interface SMTPClientConfig {
     url: string;                        // WebSocket server URL
     apiKey: string;                     // Authentication API key
+    
+    // Session Management
+    sessionTimeout?: number;            // Session timeout (default: 300000ms)
+    maxEmailsPerSession?: number;       // Emails per session (default: 10)
+    sessionBatchTimeout?: number;       // Batch wait time (default: 1000ms)
+    
+    // Connection Management  
     debug?: boolean;                    // Enable debug logging (default: false)
-    maxQueueSize?: number;              // Queue capacity limit (default: 1000)
+    maxQueueSize?: number;              // Session queue limit (default: 100)
     reconnectInterval?: number;         // Reconnect delay (default: 5000ms)
     maxReconnectAttempts?: number;      // Max retry attempts (default: 10)
     authTimeout?: number;               // Auth timeout (default: 30000ms)
     channelTimeout?: number;            // Channel timeout (default: 10000ms)
-    messageTimeout?: number;            // Message timeout (default: 60000ms)
+    messageTimeout?: number;            // SMTP command timeout (default: 60000ms)
     heartbeatInterval?: number;         // Heartbeat interval (default: 30000ms)
-    maxConcurrentMessages?: number;     // Concurrent limit (default: 1)
 }
 ```
 
 ### Transport Configuration
 
 ```typescript
-interface TransportOptions {
+interface TransportOptions extends Omit<SMTPClientConfig, 'url' | 'apiKey'> {
     host?: string;                      // Server host (default: 'api.siwatsystem.com')
     port?: number;                      // Server port (default: 443)
     secure?: boolean;                   // Use wss:// (default: true)
-    debug?: boolean;                    // Enable debug mode (default: false)
+    apiKey?: string;                    // API key for authentication
-    // ... other SMTPClientConfig options
 }
 ```
 
-## Advanced Usage
+## 🎯 Advanced Usage
 
-### Priority-Based Messaging
+### Session Priority and Options
 
 ```typescript
-import { MessagePriority } from '@siwatsystem/mxrelay-consumer';
+import { MessagePriority, SessionSendOptions } from '@siwats/mxrelay-consumer';
 
-// High priority (processed first)
+// High priority email (processed first)
-await client.sendSMTPCommand('URGENT EMAIL DATA', {
+await client.queueEmail(
+    'urgent@company.com',
+    ['admin@company.com'],
+    'Subject: URGENT ALERT\r\n\r\nSystem down!',
+    {
         priority: MessagePriority.HIGH,
-    timeout: 30000
+        timeout: 30000,
-});
+        retries: 5
+    }
+);
 
-// Critical priority (highest)
+// Critical priority email (highest priority)
-await client.sendSMTPCommand('CRITICAL ALERT EMAIL', {
+await client.queueEmail(
-    priority: MessagePriority.CRITICAL
+    'security@company.com',
-});
+    ['security-team@company.com'],
+    'Subject: SECURITY BREACH\r\n\r\nImmediate action required!',
+    {
+        priority: MessagePriority.CRITICAL,
+        immediate: true  // Skip batching, send immediately
+    }
+);
 ```
 
-### Event Monitoring
+### Session Event Monitoring
 
 ```typescript
+// Session-level events
+client.on('sessionQueued', (sessionId, queueSize) => {
+    console.log(`Session ${sessionId} queued. Queue size: ${queueSize}`);
+});
+
+client.on('sessionStarted', (sessionId, emailCount) => {
+    console.log(`Processing session ${sessionId} with ${emailCount} emails`);
+});
+
+client.on('sessionCompleted', (sessionId, results) => {
+    console.log(`Session ${sessionId} completed with ${results.length} emails`);
+});
+
+// Email-level events within sessions
+client.on('emailProcessed', (sessionId, emailId, responseTime) => {
+    console.log(`Email ${emailId} in session ${sessionId} processed in ${responseTime}ms`);
+});
+
+client.on('emailFailed', (sessionId, emailId, error) => {
+    console.error(`Email ${emailId} in session ${sessionId} failed:`, error.message);
+});
+
 // Connection events
 client.on('connected', () => console.log('WebSocket connected'));
 client.on('authenticated', () => console.log('Authentication successful'));
 client.on('disconnected', () => console.log('Connection lost'));
-
-// Queue events
-client.on('messageQueued', (messageId, queueSize) => {
-    console.log(`Message ${messageId} queued. Queue size: ${queueSize}`);
-});
-
-client.on('messageProcessed', (messageId, responseTime) => {
-    console.log(`Message ${messageId} processed in ${responseTime}ms`);
-});
-
-// Error events
-client.on('error', (error) => console.error('Client error:', error));
 ```
 
-### Statistics and Monitoring
+### Session Statistics
 
 ```typescript
 const stats = client.getStats();
-console.log('Client Statistics:', {
+console.log('Session Statistics:', {
-    messagesQueued: stats.messagesQueued,
+    sessionsQueued: stats.sessionsQueued,
-    messagesProcessed: stats.messagesProcessed,
+    sessionsProcessed: stats.sessionsProcessed,
-    messagesFailed: stats.messagesFailed,
+    sessionsFailed: stats.sessionsFailed,
-    averageResponseTime: stats.averageResponseTime,
+    emailsProcessed: stats.emailsProcessed,
+    emailsFailed: stats.emailsFailed,
+    averageSessionTime: stats.averageSessionTime,
+    averageEmailTime: stats.averageEmailTime,
     queueSize: stats.queueSize
 });
+
+console.log('Session State:', client.getSessionState()); // IDLE, PROCESSING, FAILED
+console.log('Connection State:', client.getConnectionState()); // DISCONNECTED, CONNECTED, etc.
 ```
 
-## Error Handling
+## 🛡️ Error Handling
 
-### SMTP Error Detection
+### SMTP Session Errors
-
-The transport properly detects and categorizes SMTP errors:
 
 ```typescript
 try {
-    await transporter.sendMail({
+    await client.queueEmail(
-        from: 'unauthorized@domain.com',  // Invalid sender
+        'invalid-sender@domain.com',
-        to: 'recipient@example.com',
+        ['recipient@example.com'],
-        subject: 'Test'
+        'Subject: Test\r\n\r\nTest message'
-    });
+    );
 } catch (error) {
+    if (error instanceof MessageError) {
         console.error('SMTP Error:', error.message);
-    // Output: "Sender not authorized: Sender domain not authorized for your IP or subnet"
+        console.log('Email ID:', error.messageId);
-    
+        console.log('Retry Count:', error.retryCount);
-    console.log('Error details:', {
-        smtpCode: error.context.smtpCode,        // "550"
-        rejectedRecipients: error.context.rejectedRecipients
-    });
-}
-```
-
-### Error Classification
-
-```typescript
-import { 
-    ConnectionError, 
-    AuthenticationError, 
-    MessageError,
-    TimeoutError 
-} from '@siwatsystem/mxrelay-consumer';
-
-try {
-    await client.sendSMTPCommand('MAIL FROM: <test@example.com>');
-} catch (error) {
-    if (error instanceof ConnectionError) {
-        console.error('Connection failed:', error.message);
-    } else if (error instanceof AuthenticationError) {
-        console.error('Authentication failed:', error.message);
-    } else if (error instanceof MessageError) {
-        console.error('SMTP error:', error.message, 'Code:', error.context.smtpCode);
-    } else if (error instanceof TimeoutError) {
-        console.error('Operation timed out:', error.message);
     }
 }
 ```
 
-## Connection States
+### Session State Management
 
-The client manages connection states automatically:
+The client manages session states automatically:
 
-- `DISCONNECTED` - No connection
+```mermaid
-- `CONNECTING` - Establishing WebSocket connection  
+stateDiagram-v2
-- `CONNECTED` - WebSocket connected, authentication pending
+    [*] --> IDLE
-- `AUTHENTICATING` - Sending credentials
+    IDLE --> PROCESSING: Session queued
-- `AUTHENTICATED` - Ready for SMTP operations
+    PROCESSING --> IDLE: Session completed
-- `CHANNEL_OPENING` - Opening SMTP channel
+    PROCESSING --> FAILED: Session error
-- `CHANNEL_READY` - SMTP channel active
+    FAILED --> PROCESSING: Retry session
-- `CHANNEL_CLOSED` - SMTP channel closed
+    FAILED --> IDLE: Max retries reached
-- `RECONNECTING` - Attempting reconnection
+    IDLE --> [*]: Client shutdown
-- `FAILED` - Connection failed, max retries reached
+```
 
-## Development
+- `IDLE` - No active session, ready to process
+- `PROCESSING` - Session currently being processed (mutex locked)
+- `FAILED` - Session failed, will retry or reject
+- `COMPLETED` - Session successfully completed
 
-This project uses Bun as the primary runtime. TypeScript files can be run directly without building.
+### Connection States
+
+```mermaid
+stateDiagram-v2
+    [*] --> DISCONNECTED
+    DISCONNECTED --> CONNECTING: Connect requested
+    CONNECTING --> CONNECTED: WebSocket established
+    CONNECTED --> AUTHENTICATING: Send credentials
+    AUTHENTICATING --> AUTHENTICATED: Auth successful
+    AUTHENTICATED --> CHANNEL_OPENING: Open SMTP channel
+    CHANNEL_OPENING --> CHANNEL_READY: Channel established
+    CHANNEL_READY --> CHANNEL_CLOSED: Session complete
+    CHANNEL_CLOSED --> AUTHENTICATED: Ready for next session
+    AUTHENTICATED --> DISCONNECTED: Queue empty
+    
+    CONNECTING --> RECONNECTING: Connection failed
+    AUTHENTICATING --> RECONNECTING: Auth failed
+    CHANNEL_OPENING --> RECONNECTING: Channel failed
+    RECONNECTING --> CONNECTING: Retry attempt
+    RECONNECTING --> FAILED: Max retries reached
+    
+    FAILED --> [*]: Shutdown
+    DISCONNECTED --> [*]: Shutdown
+```
+
+## 🔧 Session Queue Architecture
+
+```mermaid
+flowchart TD
+    subgraph Emails ["📧 Email Submission"]
+        E1[Email 1 - HIGH]
+        E2[Email 2 - NORMAL] 
+        E3[Email 3 - HIGH]
+        E4[Email 4 - CRITICAL]
+    end
+    
+    subgraph Queue ["📋 Session Creation"]
+        SQ[Session Queue]
+        S1[Session 1 - CRITICAL]
+        S2[Session 2 - HIGH]
+        S3[Session 3 - NORMAL]
+    end
+    
+    subgraph Processing ["⚡ Session Processing"]
+        SP[Session Processor]
+        SC[SMTP Connection]
+        SM[Session Manager]
+    end
+    
+    E1 --> SQ
+    E2 --> SQ
+    E3 --> SQ
+    E4 --> SQ
+    
+    SQ --> S1
+    SQ --> S2  
+    SQ --> S3
+    
+    S1 --> SP
+    S2 --> SP
+    S3 --> SP
+    
+    SP --> SC
+    SC --> SM
+    
+    style S1 fill:#ffcdd2
+    style S2 fill:#fff3e0
+    style S3 fill:#e8f5e8
+    style SP fill:#e1f5fe
+    style SC fill:#f3e5f5
+```
+
+## 🏭 Production Configuration
+
+### Optimal Settings
+
+```typescript
+const client = new SMTPOverWSClient({
+    url: 'wss://api.siwatsystem.com/smtp',
+    apiKey: process.env.MXRELAY_API_KEY,
+    
+    // Production optimizations
+    debug: false,
+    maxEmailsPerSession: 20,        // Batch more emails per session
+    sessionBatchTimeout: 5000,      // Wait longer to accumulate emails
+    sessionTimeout: 600000,         // 10 minute session timeout
+    maxQueueSize: 1000,             // Higher queue capacity
+    reconnectInterval: 15000,       // Longer reconnect delay
+    maxReconnectAttempts: 3,        // Fewer retries in production
+    messageTimeout: 120000          // 2 minute SMTP timeout
+});
+```
+
+### Graceful Shutdown
+
+```typescript
+process.on('SIGTERM', async () => {
+    console.log('Shutting down SMTP client...');
+    try {
+        // Wait for current sessions to complete
+        await client.shutdown(60000); // 60 second timeout
+        console.log('SMTP client shutdown complete');
+    } catch (error) {
+        console.error('Forced SMTP client shutdown');
+    }
+    process.exit(0);
+});
+```
+
+## 📚 API Reference
+
+### SMTPOverWSClient
+
+#### Methods
+- `queueEmail(from, to[], data, options?)` - Queue email for session processing
+- `getStats()` - Get session and email statistics
+- `getConnectionState()` - Get current connection state
+- `getSessionState()` - Get current session processing state
+- `getQueueSize()` - Get session queue size
+- `shutdown(timeout?)` - Graceful shutdown with session completion
+
+#### Events
+- **Session Events**: `sessionQueued`, `sessionStarted`, `sessionCompleted`, `sessionFailed`
+- **Email Events**: `emailProcessed`, `emailFailed`  
+- **Connection Events**: `connecting`, `connected`, `authenticated`, `disconnected`, `reconnecting`
+- **Queue Events**: `queueProcessingStarted`, `queueProcessingCompleted`
+- **State Events**: `stateChanged`, `error`
+
+### createTransport(apiKey, options?)
+
+Creates a Nodemailer-compatible transport with session batching.
+
+- `apiKey` - Your API key for authentication
+- `options` - Optional transport and session configuration
+
+## 🔍 Debugging
+
+### Enable Debug Logging
+
+```typescript
+const client = new SMTPOverWSClient({
+    url: 'wss://api.siwatsystem.com/smtp',
+    apiKey: 'your-api-key',
+    debug: true  // Enable comprehensive logging
+});
+
+// Debug output includes:
+// - Session creation and batching
+// - SMTP protocol commands and responses
+// - Connection state transitions
+// - Queue processing details
+// - Error stack traces
+```
+
+### Monitor Session Processing
+
+```typescript
+client.on('sessionStarted', (sessionId, emailCount) => {
+    console.log(`🚀 Starting session ${sessionId} with ${emailCount} emails`);
+});
+
+client.on('emailProcessed', (sessionId, emailId, responseTime) => {
+    console.log(`✅ Email ${emailId} processed in ${responseTime}ms`);
+});
+
+client.on('sessionCompleted', (sessionId, results) => {
+    const successful = results.filter(r => r.success).length;
+    const failed = results.filter(r => !r.success).length;
+    console.log(`🎉 Session ${sessionId} complete: ${successful} sent, ${failed} failed`);
+});
+```
+
+## 🧪 Development
 
 ### Setup
 
 ```bash
 # Clone repository
-git clone https://git.siwatsystem.com/siwat/mxrelay-consumer.git
+git clone https://git.siwatsystem.com/siwatsystem-public/mxrelay-consumer.git
 cd mxrelay-consumer
 
 # Install dependencies
 bun install
 
-# Run examples directly
+# Run examples directly (TypeScript)
 bun run examples/nodemailer-transport.ts
-
-# Run with environment variable
-MXRELAY_API_KEY=your-key bun run examples/nodemailer-transport.ts
 ```
 
 ### Build & Test
 
 ```bash
-# Build (optional - bun runs TypeScript directly)
+# Build all formats
 bun run build
 
 # Run tests
@@ -302,90 +588,15 @@ bun run lint
 bun run format
 ```
 
-## Protocol Implementation
+## 📄 License
-
-### WebSocket Message Types
-
-- `AUTHENTICATE` / `AUTHENTICATE_RESPONSE` - Authentication flow
-- `SMTP_CHANNEL_OPEN` / `SMTP_CHANNEL_READY` - Channel management  
-- `SMTP_CHANNEL_CLOSED` / `SMTP_CHANNEL_ERROR` - Channel lifecycle
-- `SMTP_TO_SERVER` / `SMTP_FROM_SERVER` - SMTP data exchange
-
-### Connection Flow
-
-1. **WebSocket Connection** - Connect to relay server
-2. **Authentication** - Authenticate using API key
-3. **Channel Management** - Open SMTP channel per message
-4. **Data Transfer** - Exchange SMTP commands and responses
-5. **Cleanup** - Close channel and disconnect when queue empty
-
-## Best Practices
-
-### Production Configuration
-
-```typescript
-const client = new SMTPOverWSClient({
-    url: 'wss://api.siwatsystem.com/smtp',
-    apiKey: process.env.MXRELAY_API_KEY,
-    
-    // Production settings
-    debug: false,
-    maxQueueSize: 5000,
-    reconnectInterval: 10000,
-    maxReconnectAttempts: 5,
-    messageTimeout: 120000
-});
-```
-
-### Graceful Shutdown
-
-```typescript
-process.on('SIGTERM', async () => {
-    console.log('Shutting down...');
-    try {
-        await client.shutdown(30000); // 30 second timeout
-        console.log('Shutdown complete');
-    } catch (error) {
-        console.error('Forced shutdown');
-    }
-    process.exit(0);
-});
-```
-
-## API Reference
-
-### createTransport(apiKey, options?)
-
-Creates a Nodemailer-compatible transport.
-
-- `apiKey` - Your API key for authentication
-- `options` - Optional transport configuration
-
-### SMTPOverWSClient
-
-Main client class for direct SMTP operations.
-
-#### Methods
-- `sendSMTPCommand(data, options?)` - Send SMTP command
-- `getStats()` - Get client statistics  
-- `getConnectionState()` - Get current state
-- `getQueueSize()` - Get queue size
-- `shutdown(timeout?)` - Graceful shutdown
-
-#### Events
-- Connection: `connecting`, `connected`, `authenticated`, `disconnected`
-- Queue: `messageQueued`, `messageProcessed`, `messageFailed`
-- State: `stateChanged`, `error`
-
-## License
 
 MIT License - see [LICENSE](LICENSE) file for details.
 
-## Support
+## 🆘 Support
 
-- Issues: [Git Repository Issues](https://git.siwatsystem.com/siwat/mxrelay-consumer/issues)
+- **Issues**: [Git Repository Issues](https://git.siwatsystem.com/siwatsystem-public/mxrelay-consumer/issues)
-- Documentation: [Project Repository](https://git.siwatsystem.com/siwat/mxrelay-consumer)
+- **Documentation**: [Project Repository](https://git.siwatsystem.com/siwatsystem-public/mxrelay-consumer)
 
 ---
 
-Built by SiwatSystem
+**Built by SiwatSystem** | *Session-based SMTP over WebSocket*

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@siwats/mxrelay-consumer",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description": "An internal TypeScript client library for transporting SMTP messages",
   "main": "lib/index.js",
   "module": "lib/index.esm.js",
@@ -27,9 +27,9 @@
     "postinstall": "npm run build",
     "build": "bun run build:cjs && bun run build:esm && bun run build:types",
     "build:cjs": "tsc -p tsconfig.cjs.json",
-    "build:esm": "echo 'ESM build disabled - use CommonJS for now'",
+    "build:esm": "tsc -p tsconfig.esm.json && cp lib-esm/index.js lib/index.esm.js && cp lib-esm/types.js lib/types.esm.js",
     "build:types": "tsc -p tsconfig.types.json",
-    "clean": "rimraf lib",
+    "clean": "rimraf lib lib-esm",
     "prepublishOnly": "npm run clean && npm run build",
     "lint": "eslint src/**/*.ts && tsc --noEmit",
     "lint:tsc": "tsc --noEmit",
@@ -61,12 +61,12 @@
   "license": "MIT",
   "repository": {
     "type": "git",
-    "url": "git+https://github.com/siwats/smtp-ws-relay-client.git"
+    "url": "git+https://git.siwatsystem.com/siwatsystem-public/mxrelay-consumer.git"
   },
   "bugs": {
-    "url": "https://github.com/siwats/smtp-ws-relay-client/issues"
+    "url": "https://git.siwatsystem.com/siwatsystem-public/mxrelay-consumer/issues"
   },
-  "homepage": "https://github.com/siwats/smtp-ws-relay-client#readme",
+  "homepage": "https://git.siwatsystem.com/siwatsystem-public/mxrelay-consumer#readme",
   "engines": {
     "node": ">=16.0.0"
   },

src/client.ts

@@ -8,13 +8,16 @@ import {
     SMTPOverWsMessage,
     SMTPOverWsMessageType,
     ConnectionState,
-    QueuedMessage,
+    SMTPSessionRequest,
+    SMTPEmail,
+    SessionResult,
+    SessionState,
     MessagePriority,
     SMTPClientConfig,
     Logger,
     ClientStats,
     ClientEvents,
-    SendOptions,
+    SessionSendOptions,
     AuthenticateMessage,
     SMTPChannelOpenMessage,
     SMTPToServerMessage,
@@ -72,20 +75,22 @@ export class SMTPOverWSClient extends EventEmitter {
     private config: Required<SMTPClientConfig>;
     private ws: WebSocket | null = null;
     private state: ConnectionState = ConnectionState.DISCONNECTED;
-    private messageQueue: QueuedMessage[] = [];
+    private sessionQueue: SMTPSessionRequest[] = [];
-    private currentMessage: QueuedMessage | null = null;
+    private currentSession: SMTPSessionRequest | null = null;
+    private sessionState: SessionState = SessionState.IDLE;
     private reconnectAttempts = 0;
     private reconnectTimer: NodeJS.Timeout | null = null;
     private authTimer: NodeJS.Timeout | null = null;
     private channelTimer: NodeJS.Timeout | null = null;
     private heartbeatTimer: NodeJS.Timeout | null = null;
-    private messageTimer: NodeJS.Timeout | null = null;
+    private sessionTimer: NodeJS.Timeout | null = null;
     private isProcessingQueue = false;
     private isShuttingDown = false;
     private logger: Logger;
     private stats: ClientStats;
     private connectionStartTime: number = 0;
-    private messageIdCounter = 0;
+    private sessionIdCounter = 0;
+    private emailIdCounter = 0;
 
     constructor(config: SMTPClientConfig) {
         super();
@@ -100,10 +105,12 @@ export class SMTPOverWSClient extends EventEmitter {
             authTimeout: 30000,
             channelTimeout: 10000,
             messageTimeout: 60000,
-            maxConcurrentMessages: 1,
+            sessionTimeout: 300000, // 5 minutes
+            maxEmailsPerSession: 10,
+            sessionBatchTimeout: 1000,
             debug: false,
             heartbeatInterval: 30000,
-            maxQueueSize: 1000,
+            maxQueueSize: 100, // sessions, not individual messages
             ...config,
             logger: config.logger || new DefaultLogger(config.debug ?? false)
         };
@@ -118,61 +125,50 @@ export class SMTPOverWSClient extends EventEmitter {
     }
 
     /**
-     * Send SMTP command with automatic queue management
+     * Queue an email for sending in a session
      */
-    public async sendSMTPCommand(data: string, options: SendOptions = {}): Promise<string> {
+    public async queueEmail(from: string, to: string[], data: string, options: SessionSendOptions = {}): Promise<string> {
         if (this.isShuttingDown) {
             throw new ShutdownError('Client is shutting down');
         }
 
         // Check queue size limit
-        if (this.messageQueue.length >= this.config.maxQueueSize) {
+        if (this.sessionQueue.length >= this.config.maxQueueSize) {
             throw ErrorFactory.queueError(
-                `Queue is full (${this.config.maxQueueSize} messages)`,
+                `Session queue is full (${this.config.maxQueueSize} sessions)`,
-                this.messageQueue.length
+                this.sessionQueue.length
             );
         }
 
-        const messageId = this.generateMessageId();
+        const emailId = this.generateEmailId();
         const priority = options.priority ?? MessagePriority.NORMAL;
-        const timeout = options.timeout ?? this.config.messageTimeout;
+        const timeout = options.timeout ?? this.config.sessionTimeout;
         const retries = options.retries ?? 3;
 
         return new Promise((resolve, reject) => {
-            const queuedMessage: QueuedMessage = {
+            const email: SMTPEmail = {
-                id: messageId,
+                id: emailId,
+                from,
+                to,
                 data,
                 resolve,
-                reject,
+                reject
-                timestamp: Date.now(),
-                retries,
-                priority
             };
 
-            // Insert message based on priority
+            // Try to add to existing session or create new one
-            this.insertMessageByPriority(queuedMessage);
+            this.addEmailToSession(email, priority, timeout, retries, options);
             
-            this.stats.messagesQueued++;
+            this.logger.debug('Email queued', {
-            this.emit('messageQueued', messageId, this.messageQueue.length);
+                emailId,
-            
+                from,
-            this.logger.debug('Message queued', {
+                to: to.length,
-                messageId,
                 priority,
-                queueSize: this.messageQueue.length,
+                queueSize: this.sessionQueue.length,
-                data: data.substring(0, 100) + (data.length > 100 ? '...' : '')
+                dataSize: data.length
             });
 
-            // Set message timeout
-            setTimeout(() => {
-                if (this.messageQueue.includes(queuedMessage) || this.currentMessage === queuedMessage) {
-                    const error = ErrorFactory.timeout('Message', timeout, { messageId });
-                    this.removeMessageFromQueue(messageId);
-                    reject(error);
-                }
-            }, timeout);
-
             // Start processing if not already running
-            if (!this.isProcessingQueue) {
+            if (!this.isProcessingQueue && this.sessionState === SessionState.IDLE) {
                 this.processQueue().catch(error => {
                     this.logger.error('Queue processing failed', error);
                 });
@@ -180,13 +176,44 @@ export class SMTPOverWSClient extends EventEmitter {
         });
     }
 
+    /**
+     * Legacy method for backward compatibility
+     * @deprecated Use queueEmail instead
+     */
+    public async sendSMTPCommand(data: string, options: any = {}): Promise<string> {
+        // Try to parse basic SMTP transaction
+        const lines = data.split('\r\n').filter(line => line.trim());
+        let from = '';
+        let to: string[] = [];
+        let messageData = '';
+        
+        for (const line of lines) {
+            if (line.startsWith('MAIL FROM:')) {
+                from = line.match(/<([^>]+)>/)?.[1] || '';
+            } else if (line.startsWith('RCPT TO:')) {
+                const recipient = line.match(/<([^>]+)>/)?.[1];
+                if (recipient) to.push(recipient);
+            } else if (line === 'DATA') {
+                // Everything after DATA is message content
+                messageData = lines.slice(lines.indexOf(line) + 1, lines.indexOf('QUIT')).join('\r\n');
+                break;
+            }
+        }
+        
+        if (!from || to.length === 0) {
+            throw new MessageError('Invalid SMTP transaction format', 'parse-error', 0);
+        }
+        
+        return this.queueEmail(from, to, messageData, options);
+    }
+
     /**
      * Get current client statistics
      */
     public getStats(): ClientStats {
         return {
             ...this.stats,
-            queueSize: this.messageQueue.length,
+            queueSize: this.sessionQueue.length,
             connectionUptime: this.connectionStartTime > 0 ? Date.now() - this.connectionStartTime : 0
         };
     }
@@ -202,22 +229,32 @@ export class SMTPOverWSClient extends EventEmitter {
      * Get current queue size
      */
     public getQueueSize(): number {
-        return this.messageQueue.length;
+        return this.sessionQueue.length;
     }
     
     /**
-     * Clear all queued messages
+     * Get current session state
      */
-    public clearQueue(): void {
+    public getSessionState(): SessionState {
-        const clearedCount = this.messageQueue.length;
+        return this.sessionState;
-        
-        // Reject all queued messages
-        for (const message of this.messageQueue) {
-            message.reject(new QueueError('Queue cleared'));
     }
 
-        this.messageQueue = [];
+    /**
-        this.logger.info('Queue cleared', { clearedCount });
+     * Clear all queued sessions
+     */
+    public clearQueue(): void {
+        const clearedCount = this.sessionQueue.length;
+        
+        // Reject all queued sessions
+        for (const session of this.sessionQueue) {
+            for (const email of session.emails) {
+                email.reject(new QueueError('Queue cleared'));
+            }
+            session.reject(new QueueError('Queue cleared'));
+        }
+        
+        this.sessionQueue = [];
+        this.logger.info('Session queue cleared', { clearedCount });
     }
 
     /**
@@ -229,7 +266,7 @@ export class SMTPOverWSClient extends EventEmitter {
         }
 
         this.isShuttingDown = true;
-        this.logger.info('Initiating client shutdown', { queueSize: this.messageQueue.length });
+        this.logger.info('Initiating client shutdown', { queueSize: this.sessionQueue.length });
 
         // Stop accepting new messages and clear timers
         this.clearTimers();
@@ -248,8 +285,8 @@ export class SMTPOverWSClient extends EventEmitter {
             this.logger.warn('Shutdown timeout reached, forcing shutdown', error);
         }
 
-        // Reject any remaining messages
+        // Reject any remaining sessions
-        this.rejectAllQueuedMessages(new ShutdownError('Client shutting down'));
+        this.rejectAllQueuedSessions(new ShutdownError('Client shutting down'));
 
         // Close connection
         await this.disconnect();
@@ -261,17 +298,18 @@ export class SMTPOverWSClient extends EventEmitter {
     }
 
     /**
-     * Process the message queue
+     * Process the session queue
      */
     private async processQueue(): Promise<void> {
-        if (this.isProcessingQueue || this.messageQueue.length === 0 || this.isShuttingDown) {
+        if (this.isProcessingQueue || this.sessionQueue.length === 0 || this.isShuttingDown || this.sessionState !== SessionState.IDLE) {
             return;
         }
 
         this.isProcessingQueue = true;
-        this.emit('queueProcessingStarted', this.messageQueue.length);
+        this.sessionState = SessionState.PROCESSING;
+        this.emit('queueProcessingStarted', this.sessionQueue.length);
         
-        this.logger.info('Queue processing started', { queueSize: this.messageQueue.length });
+        this.logger.info('Session queue processing started', { queueSize: this.sessionQueue.length });
 
         let processed = 0;
         let failed = 0;
@@ -282,109 +320,218 @@ export class SMTPOverWSClient extends EventEmitter {
                 await this.connect();
             }
 
-            // Process messages sequentially one at a time
+            // Process sessions sequentially one at a time (SMTP sessions are mutex)
-            while (this.messageQueue.length > 0 && !this.isShuttingDown) {
+            while (this.sessionQueue.length > 0 && !this.isShuttingDown) {
-                const message = this.messageQueue.shift()!;
+                const session = this.sessionQueue.shift()!;
                 
                 try {
-                    this.currentMessage = message;
+                    this.currentSession = session;
                     const startTime = Date.now();
                     
-                    await this.processMessage(message);
+                    await this.processSession(session);
                     
-                    const responseTime = Date.now() - startTime;
+                    const sessionTime = Date.now() - startTime;
-                    this.stats.messagesProcessed++;
+                    this.stats.sessionsProcessed++;
-                    this.stats.averageResponseTime = 
+                    this.stats.averageSessionTime = 
-                        (this.stats.averageResponseTime * (this.stats.messagesProcessed - 1) + responseTime) / 
+                        (this.stats.averageSessionTime * (this.stats.sessionsProcessed - 1) + sessionTime) / 
-                        this.stats.messagesProcessed;
+                        this.stats.sessionsProcessed;
                     
-                    this.emit('messageProcessed', message.id, responseTime);
+                    this.emit('sessionCompleted', session.id, []);
-                    this.logger.debug('Message processed successfully', {
+                    this.logger.debug('Session processed successfully', {
-                        messageId: message.id,
+                        sessionId: session.id,
-                        responseTime
+                        emailCount: session.emails.length,
+                        sessionTime
                     });
                     
                     processed++;
                 } catch (error) {
-                    this.stats.messagesFailed++;
+                    this.stats.sessionsFailed++;
                     this.stats.lastError = (error as Error).message;
                     this.stats.lastErrorTime = new Date();
                     
-                    this.emit('messageFailed', message.id, error as Error);
+                    this.emit('sessionFailed', session.id, error as Error);
-                    this.logger.error('Message processing failed', {
+                    this.logger.error('Session processing failed', {
-                        messageId: message.id,
+                        sessionId: session.id,
                         error: (error as Error).message
                     });
                     
                     failed++;
-                    message.reject(error as Error);
+                    session.reject(error as Error);
                 } finally {
-                    this.currentMessage = null;
+                    this.currentSession = null;
                 }
             }
 
         } catch (error) {
             this.logger.error('Queue processing error', error);
-            this.rejectAllQueuedMessages(error as Error);
+            this.rejectAllQueuedSessions(error as Error);
-            failed += this.messageQueue.length;
+            failed += this.sessionQueue.length;
         } finally {
             this.isProcessingQueue = false;
+            this.sessionState = SessionState.IDLE;
             
             // Disconnect if queue is empty and not shutting down
-            if (this.messageQueue.length === 0 && !this.isShuttingDown) {
+            if (this.sessionQueue.length === 0 && !this.isShuttingDown) {
                 await this.disconnect();
             }
             
             this.emit('queueProcessingCompleted', processed, failed);
-            this.logger.info('Queue processing completed', { processed, failed });
+            this.logger.info('Session queue processing completed', { processed, failed });
         }
     }
 
     /**
-     * Process a single message
+     * Process a single SMTP session with multiple emails
      */
-    private async processMessage(message: QueuedMessage): Promise<void> {
+    private async processSession(session: SMTPSessionRequest): Promise<void> {
-        return new Promise(async (resolve, reject) => {
+        this.logger.info('Processing SMTP session', {
+            sessionId: session.id,
+            emailCount: session.emails.length
+        });
+
+        this.emit('sessionStarted', session.id, session.emails.length);
+
         try {
-                // Open SMTP channel
+            // Open SMTP channel once for the entire session
             await this.openSMTPChannel();
             
-                // Wait for SMTP response
+            const results: SessionResult[] = [];
-                const responsePromise = this.waitForSMTPResponse(message.id);
             
-                // Send SMTP data
+            // Process each email in the session
-                this.sendSMTPData(message.data);
+            for (const email of session.emails) {
+                try {
+                    const startTime = Date.now();
                     
-                // Wait for response
+                    // Send MAIL FROM
-                const response = await responsePromise;
+                    await this.sendSMTPCommandAndWait(`MAIL FROM: <${email.from}>\r\n`);
-                message.resolve(response);
+                    
+                    // Send RCPT TO for each recipient
+                    for (const recipient of email.to) {
+                        await this.sendSMTPCommandAndWait(`RCPT TO: <${recipient}>\r\n`);
+                    }
+                    
+                    // Send DATA command
+                    await this.sendSMTPCommandAndWait('DATA\r\n');
+                    
+                    // Send message content with proper escaping
+                    const escapedData = this.escapeMessageData(email.data);
+                    await this.sendSMTPCommandAndWait(escapedData + '\r\n.\r\n');
+                    
+                    const emailTime = Date.now() - startTime;
+                    this.stats.emailsProcessed++;
+                    this.stats.averageEmailTime = 
+                        (this.stats.averageEmailTime * (this.stats.emailsProcessed - 1) + emailTime) / 
+                        this.stats.emailsProcessed;
+                    
+                    // Resolve individual email
+                    email.resolve('250 OK');
+                    
+                    const result: SessionResult = {
+                        emailId: email.id,
+                        success: true,
+                        response: '250 OK'
+                    };
+                    results.push(result);
+                    
+                    this.emit('emailProcessed', session.id, email.id, emailTime);
+                    this.logger.debug('Email processed successfully', {
+                        sessionId: session.id,
+                        emailId: email.id,
+                        emailTime
+                    });
+                    
+                } catch (error) {
+                    this.stats.emailsFailed++;
+                    
+                    // Reject individual email
+                    email.reject(error as Error);
+                    
+                    const result: SessionResult = {
+                        emailId: email.id,
+                        success: false,
+                        response: (error as Error).message,
+                        error: error as Error
+                    };
+                    results.push(result);
+                    
+                    this.emit('emailFailed', session.id, email.id, error as Error);
+                    this.logger.error('Email processing failed', {
+                        sessionId: session.id,
+                        emailId: email.id,
+                        error: (error as Error).message
+                    });
+                }
+            }
+            
+            // Send QUIT to end session
+            await this.sendSMTPCommandAndWait('QUIT\r\n');
             
             // Close SMTP channel
             await this.closeSMTPChannel();
             
-                resolve();
+            // Resolve session
+            session.resolve(results);
             
         } catch (error) {
-                // Retry logic
+            // If session-level error, retry the entire session
-                if (message.retries > 0) {
+            if (session.retries > 0) {
-                    message.retries--;
+                session.retries--;
-                    this.logger.debug('Retrying message', {
+                this.logger.debug('Retrying session', {
-                        messageId: message.id,
+                    sessionId: session.id,
-                        retriesLeft: message.retries
+                    retriesLeft: session.retries
                 });
                 
-                    // Re-queue message
+                // Re-queue session
-                    this.insertMessageByPriority(message);
+                this.insertSessionByPriority(session);
-                    resolve();
+                return;
             } else {
-                    reject(ErrorFactory.messageError(
+                throw ErrorFactory.messageError(
                     (error as Error).message,
-                        message.id,
+                    session.id,
-                        message.retries
+                    session.retries
-                    ));
+                );
             }
         }
+    }
+
+    /**
+     * Send SMTP command and wait for response
+     */
+    private async sendSMTPCommandAndWait(command: string): Promise<string> {
+        return new Promise((resolve, reject) => {
+            const timeout = setTimeout(() => {
+                reject(ErrorFactory.timeout('SMTP command', this.config.messageTimeout));
+            }, this.config.messageTimeout);
+
+            const onResponse = (message: SMTPFromServerMessage) => {
+                clearTimeout(timeout);
+                this.logger.debug('RX SMTP response', {
+                    command: command.trim(),
+                    response: message.data.trim()
                 });
+                
+                // Check if response indicates success (2xx or 3xx)
+                const responseCode = parseInt(message.data.substring(0, 3));
+                if (responseCode >= 400) {
+                    reject(new MessageError(`SMTP error: ${message.data.trim()}`, 'smtp-response', 0));
+                } else {
+                    resolve(message.data);
+                }
+            };
+
+            this.once('smtp_from_server', onResponse);
+            
+            // Send the command
+            this.sendSMTPData(command);
+        });
+    }
+
+    /**
+     * Escape message data for SMTP transmission
+     */
+    private escapeMessageData(data: string): string {
+        // Escape lines that start with a dot
+        return data.replace(/\n\./g, '\n..');
     }
 
     /**
@@ -733,7 +880,7 @@ export class SMTPOverWSClient extends EventEmitter {
         } else if (this.isProcessingQueue && !this.isShuttingDown) {
             this.logger.error('Max reconnection attempts reached');
             this.setState(ConnectionState.FAILED);
-            this.rejectAllQueuedMessages(new ConnectionError('Max reconnection attempts reached'));
+            this.rejectAllQueuedSessions(new ConnectionError('Max reconnection attempts reached'));
             this.isProcessingQueue = false;
         }
     }
@@ -809,9 +956,9 @@ export class SMTPOverWSClient extends EventEmitter {
             this.channelTimer = null;
         }
         
-        if (this.messageTimer) {
+        if (this.sessionTimer) {
-            clearTimeout(this.messageTimer);
+            clearTimeout(this.sessionTimer);
-            this.messageTimer = null;
+            this.sessionTimer = null;
         }
         
         this.stopHeartbeat();
@@ -830,54 +977,92 @@ export class SMTPOverWSClient extends EventEmitter {
     }
 
     /**
-     * Reject all queued messages
+     * Reject all queued sessions
      */
-    private rejectAllQueuedMessages(error: Error): void {
+    private rejectAllQueuedSessions(error: Error): void {
-        if (this.currentMessage) {
+        if (this.currentSession) {
-            this.currentMessage.reject(error);
+            this.currentSession.reject(error);
-            this.currentMessage = null;
+            this.currentSession = null;
         }
 
-        while (this.messageQueue.length > 0) {
+        while (this.sessionQueue.length > 0) {
-            const message = this.messageQueue.shift()!;
+            const session = this.sessionQueue.shift()!;
-            message.reject(error);
+            session.reject(error);
         }
     }
 
+
+    /**
+     * Generate unique session ID
+     */
+    private generateSessionId(): string {
+        return `session_${Date.now()}_${++this.sessionIdCounter}`;
+    }
+
     /**
-     * Insert message into queue based on priority
+     * Generate unique email ID
      */
-    private insertMessageByPriority(message: QueuedMessage): void {
+    private generateEmailId(): string {
-        let insertIndex = this.messageQueue.length;
+        return `email_${Date.now()}_${++this.emailIdCounter}`;
+    }
+
+    /**
+     * Add email to existing session or create new session
+     */
+    private addEmailToSession(email: SMTPEmail, priority: MessagePriority, timeout: number, retries: number, options: SessionSendOptions): void {
+        // Look for existing session with same priority and available space
+        let targetSession = this.sessionQueue.find(session => 
+            session.priority === priority && 
+            session.emails.length < this.config.maxEmailsPerSession
+        );
+
+        if (!targetSession) {
+            // Create new session
+            const sessionId = this.generateSessionId();
+            targetSession = {
+                id: sessionId,
+                emails: [],
+                timestamp: Date.now(),
+                retries,
+                priority,
+                resolve: (results: SessionResult[]) => {
+                    // Session-level resolve doesn't need to do anything
+                    // Individual emails handle their own resolution
+                },
+                reject: (error: Error) => {
+                    // Reject all emails in the session
+                    for (const email of targetSession!.emails) {
+                        email.reject(error);
+                    }
+                }
+            };
+
+            // Insert session based on priority
+            this.insertSessionByPriority(targetSession);
+            
+            this.stats.sessionsQueued++;
+            this.emit('sessionQueued', sessionId, this.sessionQueue.length);
+        }
+
+        // Add email to session
+        targetSession.emails.push(email);
+    }
+
+    /**
+     * Insert session into queue based on priority
+     */
+    private insertSessionByPriority(session: SMTPSessionRequest): void {
+        let insertIndex = this.sessionQueue.length;
         
         // Find insertion point based on priority
-        for (let i = 0; i < this.messageQueue.length; i++) {
+        for (let i = 0; i < this.sessionQueue.length; i++) {
-            if (message.priority > this.messageQueue[i]!.priority) {
+            if (session.priority > this.sessionQueue[i]!.priority) {
                 insertIndex = i;
                 break;
             }
         }
         
-        this.messageQueue.splice(insertIndex, 0, message);
+        this.sessionQueue.splice(insertIndex, 0, session);
-    }
-
-    /**
-     * Remove message from queue by ID
-     */
-    private removeMessageFromQueue(messageId: string): boolean {
-        const index = this.messageQueue.findIndex(msg => msg.id === messageId);
-        if (index !== -1) {
-            this.messageQueue.splice(index, 1);
-            return true;
-        }
-        return false;
-    }
-
-    /**
-     * Generate unique message ID
-     */
-    private generateMessageId(): string {
-        return `msg_${Date.now()}_${++this.messageIdCounter}`;
     }
 
     /**
@@ -910,12 +1095,15 @@ export class SMTPOverWSClient extends EventEmitter {
      */
     private initializeStats(): ClientStats {
         return {
-            messagesQueued: 0,
+            sessionsQueued: 0,
-            messagesProcessed: 0,
+            sessionsProcessed: 0,
-            messagesFailed: 0,
+            sessionsFailed: 0,
+            emailsProcessed: 0,
+            emailsFailed: 0,
             reconnectionAttempts: 0,
             totalConnections: 0,
-            averageResponseTime: 0,
+            averageSessionTime: 0,
+            averageEmailTime: 0,
             queueSize: 0,
             connectionUptime: 0
         };

src/index.ts

@@ -10,6 +10,7 @@ export {
     SMTPOverWsMessageType,
     ConnectionState,
     MessagePriority,
+    SessionState,
     type SMTPOverWsMessageBase,
     type AuthenticateMessage,
     type AuthenticateResponseMessage,
@@ -20,12 +21,14 @@ export {
     type SMTPToServerMessage,
     type SMTPFromServerMessage,
     type SMTPOverWsMessage,
-    type QueuedMessage,
+    type SMTPEmail,
+    type SMTPSessionRequest,
+    type SessionResult,
     type SMTPClientConfig,
     type Logger,
     type ClientStats,
     type ClientEvents,
-    type SendOptions
+    type SessionSendOptions
 } from './types';
 
 // Export all error classes

src/transport.ts

@@ -111,7 +111,6 @@ export class SMTPWSTransport extends EventEmitter {
             ...(this.options.authTimeout !== undefined && { authTimeout: this.options.authTimeout }),
             ...(this.options.channelTimeout !== undefined && { channelTimeout: this.options.channelTimeout }),
             ...(this.options.messageTimeout !== undefined && { messageTimeout: this.options.messageTimeout }),
-            ...(this.options.maxConcurrentMessages !== undefined && { maxConcurrentMessages: this.options.maxConcurrentMessages }),
             ...(this.options.logger !== undefined && { logger: this.options.logger }),
             ...(this.options.heartbeatInterval !== undefined && { heartbeatInterval: this.options.heartbeatInterval })
         };
@@ -169,8 +168,8 @@ export class SMTPWSTransport extends EventEmitter {
      */
     public async verify(): Promise<boolean> {
         try {
-            // Test full connection cycle: connect -> authenticate -> open SMTP -> close SMTP -> disconnect
+            // Test connection by sending a verification email with minimal data
-            await this.client.sendSMTPCommand('EHLO transport-verify\r\n');
+            await this.client.queueEmail('verify@test.local', ['verify@test.local'], 'Subject: Verification\r\n\r\nTest');
             return true;
         } catch (error) {
             const err = error as any;
@@ -216,49 +215,46 @@ export class SMTPWSTransport extends EventEmitter {
         // Get the raw message content from Nodemailer's stream
         const rawMessage = await this.getRawMessage(mail);
 
-        // Build complete SMTP transaction
+        // Prepare message data for SMTP transmission
-        let smtpTransaction = '';
-        
-        // MAIL FROM
-        smtpTransaction += `MAIL FROM: <${envelope.from}>\r\n`;
-        
-        // RCPT TO for each recipient
-        for (const recipient of envelope.to) {
-            smtpTransaction += `RCPT TO: <${recipient}>\r\n`;
-        }
-        
-        // DATA command
-        smtpTransaction += 'DATA\r\n';
-        
-        // Message content
         const messageData = this.prepareMessageData(rawMessage);
-        smtpTransaction += messageData;
 
-        // QUIT
+        try {
-        smtpTransaction += 'QUIT\r\n';
+            // Queue email using the new session-based client
+            const response = await this.client.queueEmail(envelope.from, envelope.to, messageData);
             
-        // Send complete SMTP transaction in one session
+            // Create successful result
-        const response = await this.client.sendSMTPCommand(smtpTransaction);
+            const result: SendResult = {
+                envelope,
+                messageId,
+                accepted: envelope.to.slice(), // All recipients accepted
+                rejected: [],
+                pending: [],
+                response
+            };
             
-        // Parse SMTP response for success/failure
+            return result;
-        const result = this.parseSmtpResponse(response, envelope, messageId);
+            
+        } catch (error) {
+            // Handle SMTP errors
+            const result: SendResult = {
+                envelope,
+                messageId,
+                accepted: [],
+                rejected: envelope.to.slice(), // All recipients rejected on error
+                pending: [],
+                response: (error as Error).message
+            };
             
-        // If there were SMTP errors, throw an appropriate error
-        if (result.rejected.length > 0 || !this.isSuccessfulResponse(response)) {
-            const errorDetails = this.extractSmtpError(response);
             throw new MessageError(
-                errorDetails.message, 
+                (error as Error).message, 
                 messageId, 
                 0, 
                 { 
-                    smtpCode: errorDetails.code,
+                    smtpResponse: (error as Error).message,
-                    smtpResponse: response,
+                    rejectedRecipients: envelope.to
-                    rejectedRecipients: result.rejected
                 }
             );
         }
-        
-        return result;
     }
 
     /**
@@ -329,7 +325,7 @@ export class SMTPWSTransport extends EventEmitter {
             this.emit('close');
         });
 
-        this.client.on('messageProcessed', () => {
+        this.client.on('emailProcessed', () => {
             this.emit('idle', this._isIdle);
         });
     }

src/types.ts

@@ -125,18 +125,68 @@ export enum ConnectionState {
 }
 
 /**
- * Queued message structure
+ * Individual email within a session
  */
-export interface QueuedMessage {
+export interface SMTPEmail {
+    /** Unique email ID */
     id: string;
+    /** Sender address */
+    from: string;
+    /** Recipient addresses */
+    to: string[];
+    /** Raw email message data */
     data: string;
+    /** Email-specific resolve callback */
     resolve: (response: string) => void;
+    /** Email-specific reject callback */
     reject: (error: Error) => void;
-    timestamp: number;
-    retries: number;
-    priority: MessagePriority;
 }
 
+/**
+ * SMTP session request containing multiple emails
+ */
+export interface SMTPSessionRequest {
+    /** Unique session ID */
+    id: string;
+    /** List of emails to send in this session */
+    emails: SMTPEmail[];
+    /** Session timestamp */
+    timestamp: number;
+    /** Number of retry attempts for the entire session */
+    retries: number;
+    /** Session priority */
+    priority: MessagePriority;
+    /** Session-level resolve callback */
+    resolve: (results: SessionResult[]) => void;
+    /** Session-level reject callback */
+    reject: (error: Error) => void;
+}
+
+/**
+ * Result of processing a single email in a session
+ */
+export interface SessionResult {
+    /** Email ID */
+    emailId: string;
+    /** Whether email was successfully sent */
+    success: boolean;
+    /** SMTP response for this email */
+    response: string;
+    /** Error if email failed */
+    error?: Error;
+}
+
+/**
+ * Session state enum
+ */
+export enum SessionState {
+    IDLE = 'idle',
+    PROCESSING = 'processing',
+    FAILED = 'failed',
+    COMPLETED = 'completed'
+}
+
+
 /**
  * Message priority levels
  */
@@ -172,8 +222,16 @@ export interface SMTPClientConfig {
     /** Message timeout in milliseconds */
     messageTimeout?: number;
     
-    /** Maximum number of concurrent messages */
+    /** Session timeout in milliseconds (default: 300000 = 5 minutes) */
-    maxConcurrentMessages?: number;
+    sessionTimeout?: number;
+    
+    
+    
+    /** Maximum emails per session (default: 10) */
+    maxEmailsPerSession?: number;
+    
+    /** Session batch timeout in milliseconds (default: 1000) */
+    sessionBatchTimeout?: number;
     
     /** Enable debug logging */
     debug?: boolean;
@@ -184,7 +242,7 @@ export interface SMTPClientConfig {
     /** Connection heartbeat interval in milliseconds */
     heartbeatInterval?: number;
     
-    /** Maximum queue size */
+    /** Maximum queue size (number of sessions, not individual messages) */
     maxQueueSize?: number;
 }
 
@@ -202,12 +260,15 @@ export interface Logger {
  * Client statistics
  */
 export interface ClientStats {
-    messagesQueued: number;
+    sessionsQueued: number;
-    messagesProcessed: number;
+    sessionsProcessed: number;
-    messagesFailed: number;
+    sessionsFailed: number;
+    emailsProcessed: number;
+    emailsFailed: number;
     reconnectionAttempts: number;
     totalConnections: number;
-    averageResponseTime: number;
+    averageSessionTime: number;
+    averageEmailTime: number;
     queueSize: number;
     connectionUptime: number;
     lastError?: string;
@@ -225,9 +286,12 @@ export interface ClientEvents {
     reconnecting: (attempt: number, maxAttempts: number) => void;
     reconnected: () => void;
     error: (error: Error) => void;
-    messageQueued: (messageId: string, queueSize: number) => void;
+    sessionQueued: (sessionId: string, queueSize: number) => void;
-    messageProcessed: (messageId: string, responseTime: number) => void;
+    sessionStarted: (sessionId: string, emailCount: number) => void;
-    messageFailed: (messageId: string, error: Error) => void;
+    sessionCompleted: (sessionId: string, results: SessionResult[]) => void;
+    sessionFailed: (sessionId: string, error: Error) => void;
+    emailProcessed: (sessionId: string, emailId: string, responseTime: number) => void;
+    emailFailed: (sessionId: string, emailId: string, error: Error) => void;
     queueProcessingStarted: (queueSize: number) => void;
     queueProcessingCompleted: (processed: number, failed: number) => void;
     channelOpened: () => void;
@@ -246,18 +310,25 @@ export interface ClientEvents {
 }
 
 /**
- * Message send options
+ * Session send options
  */
-export interface SendOptions {
+export interface SessionSendOptions {
-    /** Message priority */
+    /** Session priority */
     priority?: MessagePriority;
     
-    /** Message timeout in milliseconds */
+    /** Session timeout in milliseconds */
     timeout?: number;
     
-    /** Number of retry attempts */
+    /** Number of retry attempts for the entire session */
     retries?: number;
     
     /** Whether to skip queue and send immediately */
     immediate?: boolean;
+    
+    /** Maximum emails per session (default: 10) */
+    maxEmailsPerSession?: number;
+    
+    /** Session batch timeout in milliseconds (default: 1000) */
+    batchTimeout?: number;
 }
+